Double step stripping method and device therefore

Abstract

The present invention relates to a stripping method for removing species dissolved in a liquid, in particular to a method of deoxygenation of seawater, which method comprises injecting a liquid rich in dissolved species at the upper section of a stripping tower; injecting a gas entrained fluid in a first bottom part of the stripping tower, which gas being semi-lean in dissolved species, and contacting the gas being semi-lean in dissolved species with the liquid rich in dissolved species in a counter current manner in order to obtain a gas enriched in dissolved species; discharging the gas enriched in dissolved species at the upper section of the stripping tower; and discharging the liquid being depleted in the dissolved species at the bottom section of the stripping tower

Description

[0001] September 24, 2025

[0002] Stripping method

[0003] FIELD OF THE INVENTION

[0004] The present invention relates to a stripping method for removing species dissolved in a liquid, in particular to a method of deoxygenation of seawater, which method comprises injecting a liquid rich in dissolved species at the upper section of a stripping tower; injecting a gas entrained fluid in a first bottom part of the stripping tower, which gas being semi-lean in dissolved species, and contacting the gas being semi-lean in dissolved species with the liquid rich in dissolved species in a counter current manner in order to obtain a gas enriched in dissolved species; discharging the gas enriched in dissolved species at the upper section of the stripping tower; and discharging the liquid being depleted in the dissolved species at the bottom section of the stripping tower.

[0005] BACKGROUND

[0006] In many applications which make use of water it is often necessary to remove dissolved species from water prior to using the water. For example, when using seawater for injection into oil wells, it is necessary to remove oxygen or hydrogen sulfide prior to the use of the seawater to minimize corrosion of metallic parts coming into contact with the seawater. As for a further example, the removal of hydrocarbons from water is the focus of ongoing research and development.

[0007] In the state of the art, such oxygen removal is for example effected by vacuum deaeration or hydrocarbon stripping. Such devices are often big in size or high in energy consumption.

[0008] Ongoing development resulted in stripping methods for removing dissolved oxygen from the water by use of nitrogen as the stripping gas. In theory it can be any inert gas with low levels of oxygen and which does not react with the liquid. The stripping gas can be circulated in an internally closed loop by a blower or compressor while the gas is regenerated through a catalytic reactor. The same principle applies to the removal of hydrogen sulfide and hydrocarbons, but regeneration of the stripping gas may be somewhat different. By using a stripping gas being lean in the dissolved species, i.e. in the concentration of hydrogen sulfide respectively hydrocarbons, the dissolved species can be stripped, i.e. removed, from the liquid.

[0009] The EP 0 327 491 Al discloses a method of deoxygenation of water by making use of a stripping tower where gas being lean in oxygen is contacted with water to be deoxygenized in a counter current manner. The gas enriched in oxygen is subjected to a device for catalytic combustion and subsequently reintroduced into the stripping tower. The driving force for operation of the deoxygenation process is one single pump sucking the product off the stripping tower, which product stream is in a small portion used for feeding an ejector which ejector functions as means for reintroducing the gas converted in the device for catalytic combustion.

[0010] There is a need for improvements in such processes for effecting the reduction of dissolved species from water, especially for effecting deoxygenation of water. Improvements may relate to different aspects. One aim may refer to a broadening of operating conditions, i.e. to the provision of an apparatus working under extreme conditions of pressure and temperature. Further improvements may relate to the provision of an apparatus being small in size providing still good results in terms of reduction of dissolved agents.

[0011] Problems solved by the invention relate to the provision of an apparatus and a method which enables a reduction of the size of the apparatus while maintaining or improving the resulting removal of dissolved agents, in particular oxygen. The principal object of the present invention is to provide an improved process for effecting the removal of dissolved species from a liquid such as water, in particular effecting the deoxygenation of water.

[0012] SUMMARY OF THE INVENTION

[0013] The invention’s underlying problems are solved by the subject-matter of claim 1. A first aspect of the invention therefore relates to a stripping method for removing species dissolved in a liquid to obtain a stripped liquid which method comprises the steps of injecting a liquid rich in dissolved species at an upper section of a stripping tower; injecting a gas entrained fluid in the stripping tower, which gas being semi-lean in the dissolved species; contacting the gas being semi-lean in the dissolved species with the liquid rich in the dissolved species in a counter current manner in order to obtain a gas enriched in the dissolved species and a bottom liquid; discharging the gas enriched in the dissolved species at the upper section of the stripping tower; discharging the bottom liquid through an intermediate outlet provided at a second bottom part of the stripping tower, which bottom liquid is passed to an ejector; causing, in the ejector, the bottom liquid to entrain a stripping gas lean in the dissolved species to obtain the gas entrained fluid; discharging the stripped liquid through a first outlet provided at a first bottom part of the stripping tower.

[0014] The method enables the implementation of two separate steps of establishing an equilibrium between species in liquid phase and the same species in the gaseous state which enables the removal of dissolved species from the liquid. The first step is performed in the stripping tower where the gas is contacted with the liquid streaming from the top of the stripping tower downwards. The second step is performed by the ejector where bottom liquid is contacted with the gas lean in dissolved species. The ejector causes the generation of a gas entrained fluid having a large surface area between liquid and gas which again enables a second implementation of an equilibrium between dissolved species in liquid state and the gaseous state.

[0015] The method uses the bottom liquid instead of being a liquid discharged from the stripping tower as a product it is fed to the ejector for application of the second step of establishing an equilibrium between species in liquid phase and the same species in the gaseous state. In doing so, the liquid used for being passed to the ejector is not deprived from the stripping tower resulting in the fact that the two separate steps can be operated in parallel. The discharge of the finally stripped product from the stripping tower can be performed independently from the second step of establishing the equilibrium which second step makes use of the ejector. When - on the contrary thereto - the liquid used for feeding the ejector is discharged from the stripping tower before further processing, such further processing is performed with the product stream of the stripping tower and therefore at least partially performed in series. The liquid used for passing to the ejector is liquid being deprived from the product liquid in the stripping tower.

[0016] The advantage associated with performing the two separate steps of establishing the equilibrium in parallel relates to the performance of the overall removal of dissolved species.

[0017] In one aspect, the step of discharging the bottom liquid and the step of discharging the stripped liquid can be performed independently from one another. In other words, the controlling of the two steps of discharging, i.e. the discharging of the stripping tower and the discharging of bottom liquid to be passed to the ejector, are performed independently from one another. Or in other words, the two steps of discharging, i.e. the discharging of the stripping tower and the discharging of bottom liquid to be passed to the ejector, are controlled independently from one another.

[0018] Since the two separate steps of establishing the equilibrium can be performed independently from one another, the performance of removal can be improved. According to this aspect, the discharge of the stripped product can be stopped while operating the loop of discharging bottom liquid to be passed to the ejector and back to the stripping tower. This enables the improvement of the performance of removal of dissolved species.

[0019] In state-of-the-art solutions performing multiple degassing steps in serious or at least partly in serious cannot conduct multiple degassing steps independently from one another. For instance, in case of the state-of-the-art method of the EP 0 327 491 Al, the step of degassing in the stripping tower finishes with the discharging of the bottom liquid. The subsequent passing of small amounts of liquid to the ejector is implemented from the discharge conduit. A feeding of bottom liquid to the ejector cannot be performed, if no bottom liquid is discharged. There is thus no controlling of the discharging of liquid streams independently from one another. In case of the state-of-the-art method of the EP 0 327 491 Al, one single pump provided with the discharge conduit causes the driving force of operation of the degassing apparatus. By applying a high throughput power performed by the single pump, the liquid is drawn through the column. On the pressure side of the single pump, a first stream represents a discharged finished product stream and only a small partial stream branches from the discharge conduit to the ejector. The number of device units with movable parts is minimized in such a set-up, whereupon however the two separate steps of establishing the equilibrium as described above cannot be controlled independently such that the performance in terms of removal of dissolved species cannot be increased over a certain threshold.

[0020] According to the above aspect of independently controlling of the two method steps of discharging, the loop of discharging bottom liquid to the ejector and injecting the gas entrained fluid can be conducted without any discharge of the product of from the stripping tower. This enables conducting the method such that the ejector ensures the removal of the dissolved species down to a predetermined low value before the discharge of the finished product, i.e. water with a desired low concentration of dissolved species, is pursued.

[0021] In one aspect, the step of discharging the bottom liquid through the intermediate outlet and the step of discharging the stripped liquid through the first outlet is controlled such that the discharging through the intermediate outlet is performed in a higher volume per time than the discharging through the first outlet.

[0022] The beneficial effect associated with this aspect refers to the performance of removal of dissolved species. The concentration of dissolved species can be reduced. Such reduction can possibly be achieved at a low performance of the pumps reducing the problems associated with cavitation at the moving parts of the pumps.

[0023] In one aspect, the step of discharging the bottom liquid through the intermediate outlet is performed with volume streams of more than 30,000 1 / h to 80,000 1 / h, preferably 40,000 1 / h to 70,000 1 / h; and step of discharging the bottom liquid through the first outlet is performed with volume streams of 5,000 1 / h to 30,000 1 / h, preferably 10,000 1 / h to 25,000 1 / h.

[0024] The method according to claim 1 defines that the step of discharging of the bottom liquid through the intermediate outlet is performed at a second bottom part, while the step of discharging the stripped liquid through the first outlet is performed at a first bottom part. This arrangement enables a large difference in the concentration of dissolved species in the bottom section of the stripping tower. It is intended that the concentration of dissolved species in the liquid discharged through the first outlet is as low as possible, while compared to that part of the bottom section, the concentration of dissolved species in the liquid discharged through the intermediate outlet should be highest in the bottom section in order to improve the performance of the ejector in terms of removal of dissolved species. The distinction between the first bottom part and the second bottom part is understood such that the bottom liquid is withdrawn from the bottom section at two distinguishing spatial parts. Since liquids with distinguishing concentrations of dissolved species are in flow in the stripping tower, it is understood by a skilled person that the bottom liquid in the distinguishing first bottom part and second bottom part are different in terms of concentration of dissolved species. A skilled person will understand that the inlets and outlets in the bottom section may favorably be provided at places such that the respective bottom liquids at that spatial position have the most favorable constitution in terms of the concentration of dissolved species. For example, the concentration of dissolved species is favorably lowest where the outlet is provided because the finished stripped product is discharged through this outlet. On the contrary, the intermediate outlet is provided close to a position where the liquid from the bottom section of the stripping tower drops down. Therefore, the first outlet may be in the bottom plate of the bottom section and the intermediate outlet is positioned on a higher level of the bottom section.

[0025] There are several different options for implementing a large gradient in the concentration of dissolved species between the points of discharge. One option is the implementation of a separation wall disclosed below. A further option is the implementation of a relative distance of the respective outlets, which option is described as follows:

[0026] In one aspect, the step of discharging the bottom liquid from the first bottom part is performed such that the intermediate outlet and the first outlet are spaced apart by a distance of at least 10%, preferably at least 25%, more preferred at least 50% of the average diameter of the bottom section of the stripping tower; or wherein the step of discharging the bottom liquid from the first bottom part is performed such that the intermediate outlet and the first outlet are separated by a separation wall.

[0027] A skilled person will understand that the bottom section of the stripping tower has three dimensions. The two outlets for discharging the bottom liquid are not necessarily provided on the same level. It may be preferred that the discharge through the intermediate outlet is provided on a higher level than the first outlet. Especially, it may be preferred that the first outlet is positioned in the bottom plate, and the intermediate outlet is provided above the level of the bottom plate.

[0028] In the above aspect, the term “average diameter of the bottom section” is understood as follows: The bottom section comprises a part with vertically arranged stripping tower walls, wherein at that part the bottom section has a cross-sectional horizontal area, which inner diameter has either one inner diameter being concurrently the average diameter of the bottom section or the inner diameter has a largest and a smallest inner diameter, wherein the average diameter is the arithmetic medium of this largest and smallest diameter. The distance between the intermediate outlet and the first outlet enables a beneficial effect in terms of efficiency of removal of dissolved species. In one aspect, the step of injecting the gas entrained fluid in the stripping tower is performed by injecting the gas entrained fluid into the first bottom part of the stripping tower.

[0029] The beneficial effect of this aspect relates to the overall efficiency of removal of dissolved species. The liquid of the gas entrained fluid comprises the least concentration of dissolved species. This liquid is injected into the first bottom part which is the part where the first outlet is arranged.

[0030] In one aspect, the gas being semi-lean in dissolved species is separated from the gas entrained fluid, e.g. by injecting the gas entrained using a separating inlet device, such as an inlet cyclone, before being brought in contact with the liquid rich in dissolved species in a counter current manner.

[0031] In one aspect, the stripping method is a method of reducing oxygen from the liquid, i.e. the stripping method is a method of deoxygenation, wherein the liquid rich in dissolved species is an oxygen rich liquid, the stripping gas is a deoxygenated gas and the liquid being depleted in the dissolved species is a deoxygenated liquid. In other words, according to this aspect, the dissolved species is oxygen, and the method comprises a step of passing the gas enriched in oxygen to a deoxidizer and subjecting the gas enriched in oxygen to a deoxygenation to obtain the stripping gas being a deoxygenated gas, and passing the deoxygenated gas to the ejector

[0032] Thus, in one aspect, the invention relates to a method of deoxygenation of a liquid comprising the steps of injecting an oxygen rich liquid at the upper section of a stripping tower injecting a gas entrained fluid in a first bottom part of the stripping tower, which gas being semi-lean in oxygen, and contacting the gas being semi-lean in oxygen with the oxygen rich liquid in a counter current manner in order to obtain a gas enriched in oxygen; discharging the gas enriched in oxygen at the upper section of the stripping tower; discharging bottom liquid from a second bottom part of the stripping tower, passing the bottom liquid to an ejector, and causing the bottom liquid in the ejector to contact a deoxygenated gas to obtain the gas entrained fluid; discharging the deoxygenized liquid at the bottom section of the stripping tower.

[0033] In one aspect, the method is a method of deoxygenation of a liquid or a method of sulfide scavenging of a liquid or method of removing hydrocarbons from a liquid, wherein the dissolved species is one or more of oxygen, hydrogen sulfide, hydrocarbons, in particular benzene, toluene, ethylbenzene and / or xylenes.

[0034] The method makes, from a conceptual view, use of the independent adjustments of two equilibriums in view of the gases present in liquid phases. The first equilibrium is adjusted when the liquid rich in dissolved species entering the stripping tower has contact with the gas upstreaming in the stripping tower. The second equilibrium is adjusted when the bottom liquid, i.e. the liquid being subjected to the first equilibrium, has contact with the stripping gas in the ejector. The combination of gadgets required to implement the achievement of these two equilibriums is accomplished on a small scale in terms of space. In other words, the removal of dissolved species, particularly oxygen, from a liquid, particularly seawater, can be performed in a high yield on small space.

[0035] In order to enable the adjustment of the first equilibrium, i.e. the equilibrium between the liquid rich in dissolved species, in particular the oxygen rich liquid, and the gas upstreaming the stripping tower, it requires that the two phases may contact one another. This is achieved by entering the liquid rich in dissolved species, in particular the oxygen rich liquid, in the upper section of the stripping tower on the one hand, wherein on the other hand, the gas upstreaming the tower enters the stripping tower from a lower part, preferably in a bottom section, which bottom section is preferably divided into a first bottom part and a second bottom part.

[0036] The liquid subjected to the method according to the invention can be any liquid from which dissolved species, in particular oxygen, is to be removed. According to one aspect, the liquid is seawater and the dissolved species to be removed by the method of the invention is oxygen. The seawater can be directly or indirectly subjected to the method of the invention, i.e. before the seawater is subjected to the method of the invention, further means could be subjected to the seawater. In case the seawater is subjected to further means before subjecting the seawater to the method of the invention, the seawater is indirectly subjected to the method of the invention. An initial step of the method of the invention is the introduction of a liquid rich in dissolved species into the stripping tower. If the seawater is directly subjected to the method of the invention, the liquid introduced into the stripping tower is seawater. If the seawater is indirectly subjected to the method of the invention, i.e. further means are applied before, the liquid is just the liquid rich in dissolved species, i.e. rich in oxygen.

[0037] The terms “higher”, “lower”, “upper" and "bottom” are generally understood by making reference to the normal operation mode of the stripping tower, where the stripping tower has an upright position, where objects fall by gravity from a higher to a lower position.

[0038] The terms “upper section", "bottom section”, “first bottom part” and “second bottom part” are understood by its function: In order that said two phases contact one another, it requires that the liquid is introduced into the stripping tower so that gravity forces make the liquid to fall down and contact the gas. The bottom section is that part of the stripping tower where injected gas, e.g. from the gas entrained fluid, can move upwards due to thermal buoyancy. In practice, the gas can be sucked by applying negative pressure at the upper section to accelerate the upward movement of the gas to contact the falling down liquid for the stripping process.

[0039] The functional definition of the terms “upper section", "bottom section”, “first bottom part” and “second bottom part” is clear from the claims itself since the mode of operation is understood by a skilled person from the claims alone. From the above functional definition of said terms, it is immediately clear that upper section does not mean uppermost section or top of the stripping tower. Further, from the above functional definition of said terms, it is immediately clear that bottom section, first bottom part or second bottom part does not mean bottommost section first bottommost part respectively second bottommost part of the stripping tower, and not lowermost part. This becomes immediately clear because the claims comprise the term lowermost part and also bottom plate. Of course, parts of the side walls of the stripping tower represent parts of the bottom section.

[0040] The term “stripping tower” is understood by a skilled person in its ordinary meaning. It is a device that uses a gas to remove dissolved species from a liquid.

[0041] The introduction of the liquid in the upper section is performed in the upper section of the stripping tower, but it can be performed in the uppermost section or top part of the stripping tower. Further, the discharging of the deoxygenized liquid, i.e. the liquid being subjected to the stripping method, takes place at a bottom part. It can be discharged at the bottommost part or lowermost part of the stripping tower. Also, the gas enriched in dissolved species, preferably enriched in oxygen, can be discharged in the uppermost part or top part of the stripping tower. In one aspect, the gas enriched in oxygen is discharged at a position being higher than the position where the liquid to be subjected to stripping is introduced.

[0042] The “first bottom part” and the “second bottom part” represent notional spaces. According to the invention, these parts are not necessarily separated such that the respective parts represent distinguishable compartments. The vicinity of the space, where the gas entrained fluid is entered, represents the first bottom part of the stripping tower, and the vicinity of the space, where the bottom liquid is discharged, represents the second bottom part of the stripping tower. The second bottom part thus comprises a higher concentration of dissolved species, in particular oxygen, than the first bottom part. In order to benefit the most from the principal concept of having two equilibriums, it is preferred to have the discharging of the bottom liquid space as far as possible apart from the place of injecting the gas entrained fluid.

[0043] According to the invention, the liquid rich in dissolved species respectively the oxygen rich liquid is introduced into the stripping tower. This liquid is the feedstock liquid, which means that the liquid is the subject to which the method is applied. If the method is a method of deoxygenation, the liquid to be subjected to the deoxygenation is a liquid rich in oxygen. If e.g. the method is a method for reducing the H2S as a dissolved species, the liquid to be subjected to the method of the invention is a liquid rich in H2S. The term “rich” is not understood in absolute terms, but relative to at least some other liquids used in the process. The terms “liquid rich in dissolved species” or “liquid rich in oxygen” is thus a designation to distinguish these liquids from further liquids in the process. Preferably, the “liquid rich in dissolved species” is the liquid underneath all other liquids used in the process which is richest in dissolved species.

[0044] When the liquid to be subjected to the method of the invention is in fact subjected to the method of the invention, the product is obtained which product is a stripped product, so according to the invention, the product is a liquid being depleted in the dissolved species, i.e. a stripped liquid. The stripped liquid is a liquid decreased in the concentration of the species to be minimized, i.e. the concentration of the dissolved species or the concentration of oxygen.

[0045] According to the invention, the liquid being depleted in the dissolved species, in particular the deoxidized liquid, is discharged at the bottom section of the stripping tower. This is not necessarily the lowermost part of the stripping tower, but it is the part of the stripping tower where the concentration of dissolved species, in particular oxygen, is low. Thus, the stripped respectively deoxygenated liquid is preferably discharged in the first bottom part of the stripping tower. In one aspect, the discharging of the stripped liquid is discharged at the lowermost part of the stripping tower.

[0046] According to the invention, a stripping gas respectively a deoxygenated gas is used in the method of the invention. A stripping gas is low in the concentration of the species to be stripped of the liquid. A deoxygenated gas is in its broadest sense a gas with a low oxygen content. It can preferably be a gas being subjected to a step of deoxygenation. According to a preferred embodiment, the deoxygenated gas is nitrogen gas.

[0047] The stripping gas, in particular the deoxygenated gas, is introduced for stripping via the ejector. In the framework of this invention, an ejector is every device which sucks the stripping gas, in particular the deoxygenated gas, by means of the Venturi effect. The bottom liquid is passed to the ejector. In the ejector, the liquid flows in a tapered part. At the tapered part or at the end of the tapered part, there is an inlet for the stripping gas, in particular the deoxygenated gas. Since the pressure at the tapered part or at the end of the tapered part is lower (Venturi effect), the stripping gas, in particular the deoxygenated gas, is sucked in.

[0048] The ejector thus renders the bottom liquid and the stripping gas, in particular the deoxygenated gas, to become the gas entrained fluid. The second equilibrium is adjusted between the gas low in concentration of the dissolved species, in particular oxygen, and the bottom liquid. The bottom liquid is the liquid which has been subjected to the stripping during the falling down of the liquid in the stripping tower.

[0049] The gas entrained fluid comprises stripping gas and the liquid passed from the bottom part of the stripping tower to the ejector. The gas entrained fluid can be subjected to further process steps before the gas of the gas entrained fluid is provided for the step of contacting the liquid rich in dissolved species. The term “gas entrained fluid” means any kind of mixture of the respective gas with the respective liquid. In other words, it is left open if the gas is physically entrained in form of a phase distinguishing from the liquid phase or if the gas is dissolved in the liquid. When the gas separates from the liquid, a gas is provided which is semi-lean in the dissolved species and which is used for contacting with the liquid rich in dissolved species.

[0050] In one aspect, the method is a continuous method. In this aspect, the oxygen rich liquid, preferably the seawater, is continuously injected into the stripping tower and the deoxygenized liquid is continuously discharged from the stripping tower. Independently from the injecting and discharging of liquid to be treated and the treated liquid, the gas entrained fluid is continuously injected into the first bottom part of the stripping tower and the gas enriched in oxygen is continuously discharged from the stripping tower. The pressure in the stripping tower is preferably kept on a higher level than the ambient pressure, i.e. the pressure inside the stripping tower is higher than the pressure outside the stripping tower.

[0051] In one aspect, the method comprises a step of passing the gas enriched in oxygen to a deoxidizer and subjecting the gas enriched in oxygen to a deoxygenation to obtain the deoxygenated gas and passing the deoxygenated gas to the ejector.

[0052] In one aspect, the method comprises a step of passing the gas enriched in dissolved species to an absorber and subjecting the gas enriched in dissolved species to absorption to obtain the stripping gas, and passing the stripping gas to the ejector.

[0053] The deoxidizer, respectively the absorber, is a device which lowers the concentration of oxygen in the gas stream discharged at the upper section of the stripping tower. This aspect enables a closed loop of gas used for the stripping. According to a preferred aspect, the loop of stripping gas runs without adding further stripping gas to the system. According to an alternative aspect, minor amounts of stripping gas remain in the stripped liquid such that further stripping gas is to be added while the method is in operation mode.

[0054] The use of a deoxidizer, respectively the absorber, improves the method in terms of efficiency of removal of dissolved species, i.e. oxygen. In general, the concept of implementing two equilibriums improves the method. The invention’s underlaying problem of reducing size of the apparatus while maintaining the stripping efficiency is solved. The deoxidizer, respectively the absorber, improves the method even further. The concentration of oxygen in the stripping gas is minimized shortly before being used as the stripping gas. When stripping gas is used from a reservoir, diffusion of oxygen into the stripping gas may occur such that the purity of the stripping gas is slowly impaired. The preferred embodiment is thus a further improvement of the general method of the invention. For the continuous operation of the apparatus, it is not required that the apparatus supplies stripping gas to a larger extend as being present in the apparatus, because due to a preferred embodiment, the gas used for stripping is subjected to a step of separating the dissolved species from the stripping gas. Once the dissolved species is removed, the fresh stripping gas can be used for the method.

[0055] In one aspect, the step of subjecting the gas enriched in oxygen to the deoxygenation is performed by contacting the gas enriched in oxygen and a fuel, preferably a hydrogen, methanol, ethanol, ethane comprising fuel, with a catalyst. For offshore applications, the most preferred fuel is methanol. For onshore applications, the most preferred fuel is hydrogen. The step of subjecting the gas enriched in oxygen to the deoxygenation may preferably imply a step of mixing the gas enriched in oxygen with the fuel.

[0056] The catalyst is enabled to catalyze the reaction of the oxygen with the fuel. The catalyst is preferably a noble metal comprising catalyst, more preferred a Pt or Pd comprising catalyst.

[0057] In case of a stripping method for stripping H2S as the dissolved species, the stripping gas can be nitrogen or air. The gas enriched in dissolved species can be subjected to a step of absorption of H2S, preferably with carbon black, membrane filtering or other as the absorbent. In doing so, the stripping gas is deprived of H2S such that the stripping gas can be reused, i.e. the stripping gas can be passed to the ejector.

[0058] In one aspect, the step of injecting the gas entrained fluid in the stripping tower is performed by injecting the gas entrained fluid in the first bottom part of the stripping tower. According to a preferred aspect, the step of injecting the gas entrained fluid in the first bottom part of the stripping tower is performed by injecting the gas entrained fluid in the gas phase in the first bottom part.

[0059] The injection is favorably injected in the gas phase in the bottom part of the stripping tower which facilitates the separation of the gas from the liquid in the gas entrained fluid. It is to be understood that according to this aspect, the injection is performed above the level of the liquid phase in the bottom part of the stripping tower. The separation of the gas from the liquid in the gas entrained fluid can be improved by way of a cyclone. In that aspect of the invention, the gas entrained fluid is injected into a cyclone in the first bottom part, preferably above the level of the liquid phase in the bottom section, more preferred the first bottom part of the stripping tower.

[0060] In one aspect, the step of discharging the bottom liquid is performed by discharging the bottom liquid from the second bottom part of the stripping tower. The second bottom part of the stripping tower is the part of the stripping tower, where the liquid is located which liquid has been subjected to the first equilibrium. This liquid, i.e. the bottom liquid, is passed to the ejector. Before being processed in the ejector, the bottom liquid can be subjected to a further step. In other words, the method of the invention may comprise further steps between the steps of subjecting the liquid to the first equilibrium and causing the bottom liquid to contact the stripping gas. In case such further steps are performed, it is the “treated bottom liquid” being caused to contact the stripping gas.

[0061] In one aspect, the first bottom part of the stripping tower and the second bottom part of the stripping tower are separated from one another by the separation wall. The separation wall may divide the bottom section of the stripping tower into two chamber, i.e. the first bottom part may become a first bottom chamber and the second bottom part may become a second bottom chamber.

[0062] A person skilled in the art understands the term “separation wall” in the broadest sense as means separating the first and second bottom part, i.e. the first bottom part of the stripping tower and the second bottom part of the stripping tower are separated from one another by means for separation. According to a preferred aspect, the separation wall is arranged on the bottom plate. According to a more preferred aspect, the separation wall is arranged such that the cross-sectional area of the second bottom chamber increases in direction towards the upper section of the stripping tower. This more preferred aspect may be accomplished such that the separation wall is arranged such that it forms a kind of funnel. This set-up of the separation wall in the stripping tower enables the liquid flowing downwards the stripping tower passes into the second bottom chamber. From the second bottom chamber, the liquid is discharged and passed to the ejector.

[0063] The separation wall renders the first bottom part and the second bottom part to become a first bottom chamber resp. second bottom chamber. When a separation wall is implemented in the stripping tower, the step of discharging of the bottom liquid is performed from the second bottom chamber and the step of injecting the gas entrained fluid is performed in the first bottom chamber. The step of injecting the gas entrained fluid in the first bottom chamber may be performed such that the liquid of the gas entrained fluid passes into the first bottom chamber at a place above the level of the liquid in the first bottom chamber. The first orifice or the cyclone releasing the gas entrained fluid is arranged such that the liquid phase of the gas entrained fluid flows into the first bottom chamber.

[0064] It is also to be understood that the first bottom part of the stripping tower and the second bottom part of the stripping tower may separated from one another by a pipe like construction inside the stripping tower, i.e. that the separation wall is circular in shape.

[0065] In one aspect, the step of discharging the liquid being depleted in the dissolved species, in particular the deoxygenized liquid is performed at the first bottom part / chamber of the stripping tower. The liquid in the first bottom part / chamber contains the least concentration of dissolved species, in particular oxygen. The step of discharging can be performed at the bottommost part of the first bottom part / chamber.

[0066] In one aspect, the liquid is sea water. The liquid can be subjected to a further treatment before the liquid is introduced as liquid rich in dissolved species respectively as liquid rich in oxygen into the stripping tower. After the seawater being subjected to the methods of the invention, the liquid produced by methods according to the invention is deprived of the dissolved species, in particular deprived of oxygen. The liquid can be subjected to further treatments or can be used for the application offshore or onshore.

[0067] The invention’s underlying problems are further solved by the subject-matter of claim 11. A second aspect of the invention therefore relates to an apparatus for stripping a liquid comprising a stripping tower comprising in the upper section a first inlet for a liquid to be subjected to stripping, in a bottom section a first outlet for discharging a stripped liquid, and in the bottom section a first bottom part and a second bottom part; a main orifice for discharging a gas enriched in dissolve species or a first gaseous fluid conduit; an ejector; a source for a stripping gas; a second gaseous fluid conduit connecting the ejector and the source for the stripping gas; a gas entrained fluid conduit connecting the ejector and the first bottom part; and a liquid fluid conduit connecting the ejector and the second bottom part via an intermediate outlet.

[0068] The apparatus enables a stripping of dissolved species in a liquid which stripping is performed by implementing two separate equilibriums between species dissolved in a liquid phase and present in a gaseous phase. The intermediate outlet enables the discharge of bottom liquid from the stripping tower in order to be passed to a second step of stripping caused by an ejector. The liquid to be deprived of dissolved species is not withdrawn from the stripping tower as a product stream. The apparatus performs two separate stripping steps as parallel steps.

[0069] In one aspect, the liquid fluid conduit is provided with a pump for discharging liquid from the second bottom part to the ejector or the first outlet is provided with a pump for discharging the stripped liquid. In a further aspect, the liquid fluid conduit is provided with a pump for discharging liquid from the second bottom part to the ejector and the first outlet is provided with a pump for discharging the stripped liquid.

[0070] This feature enables the apparatus to independently perform the step pursued by the ejector on the one hand and the discharge of the stripped product, i.e. the final product, on the other hand.

[0071] The apparatus for stripping a liquid is preferably an apparatus for deoxygenation of a liquid. In that case, the apparatus is used for depriving dissolved species from the liquid, wherein the dissolved species is oxygen, the liquid is subjected to a stripping to obtain a stripped liquid and the deoxygenated gas is the stripping gas. In the preferred apparatus, where the dissolved species is oxygen, the second aspect of the invention thus relates to an apparatus for deoxygenation of a liquid comprising a stripping tower comprising in the upper section a first inlet for a liquid to be subjected to stripping, in a bottom section a first outlet for discharging a stripped liquid, and in the bottom section a first bottom part and a second bottom part; a main orifice for discharging a gas enriched in dissolved species or a first gaseous fluid conduit; an ejector; a gas entrained fluid conduit connecting the ejector and the first bottom part and a liquid fluid conduit connecting the ejector and the second bottom part..

[0072] The apparatus is a device minimized in size while remaining the efficiency of removal of dissolved species. The combination of the two gadgets stripping tower and ejector contribute to the beneficial effects provided with the apparatus according to the invention.

[0073] In one aspect, apparatus further comprises a source for a stripping gas; a second gaseous fluid conduit connecting the ejector and the source for the stripping gas. For the continuous operating of the apparatus, it is not required that the apparatus supplies stripping gas to a larger extend as being present in the apparatus, because due to a preferred embodiment, the gas used for stripping is subjected to a step of separating the dissolved species from the stripping gas. Once the dissolved species is removed, the fresh stripping gas can be used for the method.

[0074] The main orifice for discharging a gas enriched with dissolved species, in particular oxygen, is arranged in the upper section of the stripping tower. Alternatively to the main orifice, there is provided a first gaseous fluid conduit, which is provided for passing the gas to a further unit, e.g. to the deoxidizer used according a preferred embodiment. The first gaseous fluid conduit can be made suitable for discharging the gas enriched in dissolved species, in particular oxygen.

[0075] In one aspect, the source for deoxygenated gas or stripping gas can be a reservoir from which the gas is provided.

[0076] In one aspect, the apparatus further comprises a deoxidizer as a source for deoxygenated gas, wherein the first gaseous fluid conduit connecting the deoxidizer and the stripping tower, and wherein the second gaseous fluid conduit connecting the ejector and the deoxidizer.

[0077] The deoxidizer is a unit which reduces the oxygen from the gas enriched in oxygen being passed from the stripping tower to the deoxidizer. The deoxidizer enables the reduction of oxygen from the stripping gas to an concentration of less than 10 ppb.

[0078] In one aspect, the gas entrained fluid conduit has a second inlet into the first bottom part, wherein distance of the second inlet to the first outlet is smaller than the distance of the second inlet to the intermediate outlet; or wherein the intermediate outlet and the second inlet are separated by a separation wall.

[0079] The gas entrained fluid conduit and the liquid fluid conduit form the connections between the stripping tower and the ejector. Within the stripping tower, the second inlet at which the gas entrained fluid enters the bottom section of the stripping tower should be close to the first outlet and the second inlet should be spaced apart from the intermediate outlet. Further, the second inlet should be space apart from the intermediate outlet in order to prevent that liquid from the gas entrained fluid is sucked in the liquid fluid conduit, which liquid is low in concentration of dissolved species. In other words, this aspect minimizes a shortcut which reduces the effectiveness of the ejector. This aspect of the invention affects in particular those cases where no separation wall between the first and second bottom part is arranged. According to an alternative, the intermediate outlet and the second inlet are separated by a separation wall. This alternative ensures that no liquid being relatively lean in dissolved species enters the intermediate outlet, which in turn improves the efficiency of stripping process.

[0080] In one aspect, the intermediate outlet and the first outlet are spaced apart by a distance of at least 10%, preferably at least 25%, more preferred at least 50% of the average diameter of the bottom section of the stripping tower. In view of the understanding of the term “average diameter”, reference is made to the description above.

[0081] In one aspect, the first outlet for the stripped, in particular deoxygenized liquid is arranged in fluid connection with the first bottom part, preferably wherein the first outlet for the stripped, in particular deoxygenized liquid is arranged in fluid connection with the second bottom part close to the lowermost part or at the lowermost part of the second bottom part.

[0082] The first bottom part is the part in the stripping tower comprising the liquid being subjected twice to the adjustment of an equilibrium between liquid and gas phase. It is thus preferred discharging the stripped liquid from that part of the stripping tower. It is not required that the outlet is arranged at the lowermost part of the first bottom part, but it may be arranged there.

[0083] The apparatus according to the invention can be used for stripping H2S as dissolved species. In one aspect, the apparatus further comprises as a source for stripping gas an H2S absorber comprising e.g. carbon black as the absorbing material. According to that aspect, the first gaseous fluid conduit connects the stripping tower with the absorber and the second gaseous fluid conduit connects the absorber with the ejector.

[0084] In one aspect, the cross-section area of the bottom part of the stripping tower is larger than the cross-section area of the upper part of the stripping tower. This aspect is preferred for the arrangement of a first bottom part / chamber and second bottom part / chamber in the stripping tower.

[0085] In one aspect, the apparatus further comprises means for separation, such as a separation wall. In this aspect, the first bottom part of the stripping tower and the second bottom part of the stripping tower are divided from one another by the separation wall extending from the bottom plate of the stripping tower to a height of the stripping tower not exceeding 2 / 3, preferably 1 / 2, more preferred 1 / 3, of the total height of the inner volume of the stripping tower.

[0086] The separation wall is attached to the bottom plate of the stripping tower in order to liquid tight separate the first bottom chamber and second bottom chamber from one another. The height of the separation wall relative to the total height of the inner volume of the stripping tower influences the volume of the bottom chambers and the height of the stripping pathway where the upstreaming gas contacts the liquid introduced in the upper section of the stripping tower. The preferred relative height is favorable for achieving high yields in removal of dissolved species.

[0087] In one aspect, at an upper level of the separation wall, the cross-section area of the second bottom chamber is larger than the cross-section area of the first bottom chamber; and / or wherein, at the upper level of the separation wall, the cross-section area of the second bottom chamber is larger than the cross-section area of the second bottom chamber at lower level of the separation wall.

[0088] The upper level of the separation wall represents the highest level of the separation wall in the stripping tower. The separation wall together with the walls of the stripping tower define an area when regarding the cross-section at the height of the upper level. Further, the separation wall together with the walls of the stripping tower define an area when regarding the cross-section at the level of the bottom plate. In the above aspects, the separation wall is favorably arranged such that the separation wall forms a kind of a funnel such that the streams can flow in a favorable manner.

[0089] In one aspect, the stripping tower comprises in the upper part a second outlet for a gas which second outlet being connected to the first gaseous fluid conduit. The gas enriched in dissolved species, in particular oxygen, can be released from the stripping tower. In case the gas is recycled via deoxidizer or absorber, the gas enriched in dissolved species, in particular oxygen is discharged from the second outlet at the upper part of the stripping tower and passed through the first gaseous fluid conduit to the deoxidizer or absorber.

[0090] In one aspect, the deoxygenator comprises a fuel inlet and a catalyst suitable for a reaction of the fuel with the oxygen in the gas. In order to operate the deoxygenator, it requires the provision of fuel. The fuel is passed to the deoxygenator via a fuel inlet. Features being solely disclosed in connection with the methods of the invention are deemed to be disclosed in connection with the apparatus of the invention and vice versa.

[0091] BRIEF DESCRIPTION OF THE DRAWING

[0092] Certain aspects of the presently disclosed subject-matter will be described with reference to the accompanying drawing, which is representative and schematic in nature and is not considered to be limiting in any respect as it relates to the scope of the subject-matter disclosed herein:

[0093] Figure 1 depicts the principle set up of the apparatus of the invention;

[0094] Figure 2 depicts an example of the apparatus of the invention;

[0095] Figure 3 depicts an example of the top view onto the cross-section of the stripping tower along the lines A to B shown in Fig. 2; and

[0096] Figure 4 depicts the principle of the ejector used according to the invention.

[0097] DESCRIPTION OF EMBODIMENTS

[0098] Fig. 1 shows the principle set up of the apparatus of the invention. A liquid being supposed for subjected to a degassing enters a stripping tower 1 through a first inlet. In the stripping tower 1, the liquid contacts a stripping gas in a counter current stream. A first equilibrium is adjusted between the downstreaming liquid and the upstreaming gas. The gas present in the liquid and to be removed moves from the liquid phase to the gas phase. The gas is discharged from the stripping tower 1 at a second outlet 9.

[0099] From the second bottom part 5 bottom liquid is discharged and passed via liquid fluid conduit 13 to ejector 15, where stripping gas enters via the second gaseous fluid conduit 11. In the ejector 15, the stripping gas together with the bottom liquid form the gas entrained fluid passed via gas entrained fluid conduit 12 back into the stripping tower 1. This loop from the stripping tower back to the stripping tower represents the pass where the second equilibrium is adjusted. The gas from the gas entrained fluid moves upward in the stripping tower. The liquid from the gas entrained fluid drops into the first bottom part 4 of the stripping tower 1. From that part, the stripped liquid can be discharged via the first outlet.

[0100] In practice, the stripping tower 1 is partially filled with seawater and the method according to the invention is started with introduction of stripping gas and further seawater. The pressure in the stripping tower 1 is higher than outside the stripping tower. The method is operated continuously.

[0101] Figure 2 shows the preferred embodiments, where a deoxidizer 14 is used and where a separation wall 6 is used. Instead of having an orifice as the second outlet 9 for discharging the gas from the first equilibrium, there is provided the first gaseous fluid conduit 10 passing the gas to the deoxidizer 14. Therein the oxygen is removed from the gas. The gas essentially being devoid of oxygen is used then as the stripping gas and passed via second gaseous fluid conduit to the ejector 15. A pump 16 pumps the bottom liquid into the ejector 15

[0102] The separation wall makes the first bottom part to be the first bottom chamber 4 and the second bottom part to be the second bottom chamber 5. The gas entrained fluid is injected into the first bottom chamber. In practice, this can be performed by a cyclone arranged above the liquid level in the first bottom chamber 4. The liquid flowing downward flows into the second bottom chamber 5 from which the bottom fluid is discharged for being subjected to the ejector 15.

[0103] Figure 2 shows the upper level 6a of the separation wall 6. The cross section line A-B crosses the upper level of the separation wall. Figure 3 shows the top view onto that cross-section. In a preferred embodiment, the separation wall 6 is formed such that it forms a kind of a funnel. The cross sectional area of the second bottom chamber 5 along the line A-B is higher than the cross sectional area of the first bottom chamber 4 along the line A-B. The liquid flowing downward is collected by this funnel. Also, the separation wall 6 can be tilted such that the separation wall 6 is not aligned vertically. In this case, the cross sectional area of the second bottom chamber 5 is higher at the height of the line A-B than the cross sectional area of the bottom chamber 5 at the height of the bottom plate.

[0104] Figure 4 shows an example of an ejector 15. The bottom liquid enters the ejector through inlet 18, the stripping gas enters the ejector through inlet 17. The bottom liquid inlet conduit forms a nozzle which tapering results in a lowering of the pressure perpendicular to the flowing bottom liquid such that the stripping gas is sucked in. At the gas entrained fluid outlet 19, the gas entrained fluid leaves the ejector 15.

[0105] The following items are disclosed herewith as exemplary embodiments:

[0106] 1. A stripping method for removing species dissolved in a liquid to obtain a stripped liquid comprising the steps of

[0107] - injecting a liquid rich in dissolved species at an upper section (2) of a stripping tower (i);

[0108] - injecting a gas entrained fluid in the stripping tower (1), which gas being semi-lean in the dissolved species; - contacting the gas being semi-lean in the dissolved species with the liquid rich in the dissolved species in a counter current manner in order to obtain a gas enriched in the dissolved species and a bottom liquid;

[0109] - discharging the gas enriched in the dissolved species at the upper section (2) of the stripping tower (1);

[0110] - discharging the bottom liquid of the stripping tower (1), and passing the bottom liquid to an ejector (15);

[0111] - causing, in the ejector (15), the bottom liquid to entrain a stripping gas lean in the dissolved species to obtain the gas entrained fluid;

[0112] - discharging the stripped liquid of the stripping tower (1). la. A stripping method for removing species dissolved in a liquid to obtain a stripped liquid comprising the steps of

[0113] - injecting a liquid rich in dissolved species at an upper section (2) of a stripping tower (i);

[0114] - injecting a gas entrained fluid in the stripping tower (1), which gas being semi-lean in the dissolved species;

[0115] - contacting the gas being semi-lean in the dissolved species with the liquid rich in the dissolved species in a counter current manner in order to obtain a gas enriched in the dissolved species and a bottom liquid;

[0116] - discharging the gas enriched in the dissolved species at the upper section (2) of the stripping tower (1);

[0117] - discharging the bottom liquid through an intermediate outlet (20), which bottom liquid is passed to an ejector (15);

[0118] - causing, in the ejector (15), the bottom liquid to entrain a stripping gas lean in the dissolved species to obtain the gas entrained fluid; discharging the stripped liquid through a first outlet (8).

[0119] 2. The stripping method of item 1 or item la, wherein the gas being semi-lean in dissolved species is separated from the gas entrained fluid, e.g. by injecting the gas entrained fluid using a separating inlet device, such as an inlet cyclone, before being brought in contact with the liquid rich in dissolved species in a counter current manner.

[0120] 3. The method according to any one of the preceding items, wherein the method is a method of deoxygenation of a liquid or a method of sulfide scavenging of a liquid or method of removing dissolved hydrocarbons from a liquid, wherein the dissolved species is one or more of oxygen, hydrogen sulfide, hydrocarbons, in particular benzene, toluene, ethylbenzene and / or xylenes.

[0121] 4. The method according to any one of the preceding items, wherein the dissolved species is oxygen, and the method comprises a step of passing the gas enriched in oxygen to a deoxidizer (14) and subjecting the gas enriched in oxygen to deoxygenation to obtain the stripping gas lean in oxygen and passing the gas lean in oxygen to the ejector (15).

[0122] 5. The method according to item 4, wherein the step of subjecting the gas enriched in oxygen to the deoxygenation is performed by contacting the gas enriched in oxygen and a fuel, preferably a hydrogen, methanol, ethanol, methane comprising fuel, with a catalyst. 6. The method according to any one of the preceding items, wherein the step of injecting the gas entrained fluid in the stripping tower (1) is performed by injecting the gas entrained fluid in a first bottom part (4) of the stripping tower (1); and / or wherein the step of discharging the bottom liquid is performed by discharging the bottom liquid from a second bottom part (5) of the stripping tower (1).

[0123] 7. The method according to any one of the preceding items, wherein the stripping tower comprises a separation wall, preferably wherein the first bottom part (4) of the stripping tower (1) and the second bottom part (5) of the stripping tower (1) are separated from one another by the separation wall (6), preferably wherein the separation wall (6) is arranged on a bottom plate of the stripping tower (1) such that the cross-sectional area of the second bottom part (5) increases in direction towards the upper section (2) of the stripping tower.

[0124] 8. The method according to any one of the preceding items, wherein the step of discharging the stripped liquid is performed at a bottom section (3) of the stripping tower (1), preferably wherein the step of discharging the stripped liquid is performed at the first bottom part (4) of the bottom section (3) of the stripping tower (1).

[0125] 9. An apparatus for stripping a liquid comprising

[0126] - a stripping tower (1) comprising in the upper section (2) a first inlet (7) for a liquid to be subjected to stripping, in a bottom section (3) a first outlet (8) for discharging a stripped liquid, and in the bottom section (3) a first bottom part (4) and a second bottom part (5);

[0127] - a main orifice for discharging a gas enriched in dissolved species or a first gaseous fluid conduit (10);

[0128] - an ejector (15);

[0129] - a gas entrained fluid conduit (12) connecting the ejector (15) and the first bottom part

[0130] (4) and a liquid fluid conduit (13) connecting the ejector (15) and the second bottom part

[0131] (5).

[0132] 10. Apparatus according to item 9, wherein the apparatus further comprises

[0133] - a source for a stripping gas;

[0134] - a second gaseous fluid conduit (11) connecting the ejector (15) and the source for the stripping gas.

[0135] 11. Apparatus according to item 9 or item 10, wherein the apparatus is an apparatus for deoxygenation of a liquid, which apparatus further comprises a deoxidizer (14) as a source for deoxygenated gas, wherein the first gaseous fluid conduit (10) connecting the deoxidizer (14) and the stripping tower (1), and wherein the second gaseous fluid conduit (11) connecting the ejector (15) and the deoxidizer (14).

[0136] 12. Apparatus according to any one of items 9 to 11, wherein the gas entrained fluid conduit (12) has a first orifice in the first bottom part (5) and the liquid fluid conduit (13) has a second orifice in the second bottom part (6), wherein first orifice and second orifice have a distance of at least half the diameter of the bottom section (3) of the stripping tower (1). 13. Apparatus according to any one of items 9 to 12, wherein the first outlet (8) for the deoxygenized liquid is arranged in fluid connection with the first bottom part (4), preferably wherein the first outlet (8) for the deoxygenized liquid is arranged in fluid connection with the second bottom part (5) close to the lowermost part or at the lowermost part of the second bottom part (5).

[0137] 14. Apparatus according to any one of item 9 or item 13, wherein the cross-section area of the bottom part (3) of the stripping tower (1) is larger than the cross-section area of the upper part (2) of the stripping tower (1).

[0138] 15. Apparatus according to any one of items 9 to 14, wherein the stripping tower further comprises means for separating (6) the first bottom part (4) of the stripping tower (1) and the second bottom part (5) of the stripping tower (1) to obtain a first bottom chamber (4) and a second bottom chamber (5).

[0139] 16. Apparatus according to item 15, wherein the means for separating (6) the first bottom part (4) of the stripping tower (1) and the second bottom part (5) of the stripping tower extends from the bottom plate of the stripping tower (1) to a height of the stripping tower (1) not exceeding 2 / 3, preferably 1 / 2, more preferred 1 / 3, of the total height of the inner volume of the stripping tower (1).

[0140] 17. Apparatus according to item 15 or item 16, wherein the means for separating (6) the first bottom part (4) of the stripping tower (1) and the second bottom part (5) of the stripping tower is a separation wall (6), and at an upper level (6a) of the separation wall (6), the cross-section area of the second bottom chamber (5) is larger than the crosssection area of the first bottom chamber (4); and / or wherein, at the upper level (6a) of the separation wall (6), the cross-section area of the second bottom chamber (5) is larger than the cross-section area of the second bottom chamber (5) at lower level of the separation wall (6).

[0141] REFERENCE LIST

[0142] 1 Stripping tower

[0143] 2 upper section of stripping tower

[0144] 3 bottom section of stripping tower

[0145] 4 first bottom part / chamber

[0146] 5 second bottom part / chamber

[0147] 6 separation wall

[0148] 6a upper level of separation wall

[0149] 7 first inlet

[0150] 8 first outlet

[0151] 9 second outlet

[0152] 10 first gaseous fluid conduit

[0153] 11 second gaseous fluid conduit

[0154] 12 gas entrained fluid conduit

[0155] 13 liquid fluid conduit

[0156] 14 deoxidizer

[0157] 15 ejector

[0158] 16 pump

[0159] 17 stripping gas inlet of ejector

[0160] 18 bottom liquid inlet of ejector

[0161] 19 gas entrained fluid outlet of ejector

[0162] 20 intermediate outlet

[0163] 21 pump for discharging stripped liquid

Claims

AMENDED CLAIMS 1 TO 211. A stripping method for removing species dissolved in a liquid to obtain a stripped liquid comprising the steps of- injecting a liquid rich in dissolved species at an upper section (2) of a stripping tower (1);- injecting a gas entrained fluid in the stripping tower (1), which gas being semilean in the dissolved species;- contacting the gas being semi-lean in the dissolved species with the liquid rich in the dissolved species in a counter current manner in order to obtain a gas enriched in the dissolved species and a bottom liquid;- discharging the gas enriched in the dissolved species at the upper section (2) of the stripping tower (1);- discharging the bottom liquid through an intermediate outlet (20) provided at a second bottom part (5) of the stripping tower (1), which bottom liquid is passed to an ejector (15);- causing, in the ejector (15), the bottom liquid to entrain a stripping gas lean in the dissolved species to obtain the gas entrained fluid;- discharging the stripped liquid through a first outlet (8) provided at a first bottom part (4) of the stripping tower (1).

2. The method according to claim 1, wherein the step of discharging the bottom liquid and the step of discharging the stripped liquid can be performed independently from one another.

3. The method according to claim 1 or claim 2, wherein the step of discharging the bottom liquid from the first bottom part (4) is performed such that the intermediate outlet (20) and the first outlet (8) are spaced apart by a distance of at least 10%, preferably at least 25%, more preferred at least 50% of the average diameter of the bottom section (3) of the stripping tower (1); or wherein the step of discharging the bottom liquid from the first bottom part (4) is performed such that the intermediate outlet (20) and the first outlet (8) are separated by a separation wall (6).

4. The method according to any one of the preceding claims, wherein the step of injecting the gas entrained fluid in the stripping tower (1) is performed by injecting the gas entrained fluid into the first bottom part (4) of the stripping tower (1).

5. The method according to any one of the preceding claims, wherein the gas being semi-lean in dissolved species is separated from the gas entrained fluid, preferably by injecting the gas entrained fluid using a separating inlet device, such as an inlet cyclone, before being brought in contact with the liquid rich in dissolved species in a counter current manner.

6. The method according to any one of the preceding claims, wherein the method is a method of deoxygenation of a liquid or a method of sulfide scavenging of a liquid or method of removing dissolved hydrocarbons from a liquid, wherein the dissolved species is one or more of oxygen, hydrogen sulfide, hydrocarbons, in particular benzene, toluene, ethylbenzene and / or xylenes.

7. The method according to any one of the preceding claims, wherein the dissolved species is oxygen, and the method comprises a step of passing the gas enriched in oxygen to a deoxidizer (14) and subjecting the gas enriched in oxygen to deoxygenation to obtain the stripping gas lean in oxygen and passing the gas lean in oxygen to the ejector (15).

8. The method according to claim 7, wherein the step of subjecting the gas enriched in oxygen to the deoxygenation is performed by contacting the gas enriched in oxygen and a fuel, preferably a hydrogen, methanol, ethanol, methane comprising fuel, with a catalyst.

9. The method according to any one of the preceding claims, wherein the first bottom part (4) of the stripping tower (1) and the second bottom part (5) of the stripping tower (1) are separated from one another by the separation wall (6), preferably wherein the separation wall (6) is arranged on a bottom plate of the stripping tower (1) such that the cross-sectional area of the second bottom part (5) increases in direction towards the upper section (2) of the stripping tower.

10. The method according to any one of the preceding claims, wherein the step of discharging the stripped liquid is performed at a bottom section (3) of the stripping tower (1), preferably wherein the step of discharging the stripped liquid is performed at the first bottom part (4) of the bottom section (3) of the stripping tower (1).

11. An apparatus for stripping a liquid comprising• a stripping tower (1) comprising in the upper section (2) a first inlet (7) for a liquid to be subjected to stripping, in a bottom section (3) a first outlet (8) for discharging a stripped liquid, and in the bottom section (3) a first bottom part (4) and a second bottom part (5); a main orifice for discharging a gas enriched in dissolved species or a first gaseous fluid conduit (10);an ejector (15);• a gas entrained fluid conduit (12) connecting the ejector (15) and the first bottom part (4) and a liquid fluid conduit (13) connecting the ejector (15) and the second bottom part (5) via an intermediate outlet (20).

12. Apparatus according to claim 11, wherein the liquid fluid conduit (13) is provided with a pump for discharging liquid from the second bottom part (5) to the ejector (15) and the first outlet is provided with a pump for discharging the stripped liquid.

13. Apparatus according to claim 11 or claim 12, wherein the apparatus further comprises• a source for a stripping gas;• a second gaseous fluid conduit (11) connecting the ejector (15) and the source for the stripping gas.

14. Apparatus according to any one of claims 11 to 13, wherein the apparatus is an apparatus for deoxygenation of a liquid, which apparatus further comprises a deoxidizer (14) as a source for deoxygenated gas, wherein the first gaseous fluid conduit (10) connecting the deoxidizer (14) and the stripping tower (1), and wherein the second gaseous fluid conduit (11) connecting the ejector (15) and the deoxidizer (14).

15. Apparatus according to any one of claims 11 to 14, wherein the gas entrained fluid conduit (12) has a second inlet into the first bottom part (4), wherein distance of the second inlet to the first outlet (8) is smaller than the distance of the second inlet to the intermediate outlet (20); or wherein the intermediate outlet (20) and the second inlet are separated by a separation wall (6).

16. Apparatus according to any one of claims 11 to 15, wherein the first outlet (8) for the deoxygenized liquid is arranged in fluid connection with the first bottom part (4), preferably wherein the first outlet (8) for the deoxygenized liquid is arranged in fluid connection with the second bottom part (5) close to the lowermost part or at the lowermost part of the second bottom part (5).

17. Apparatus according to any one of claims 11 to claim 16, wherein the crosssection area of the bottom part (3) of the stripping tower (1) is larger than the cross-section area of the upper part (2) of the stripping tower (1).

18. Apparatus according to any one of claims 11 to 17, wherein the stripping tower further comprises means for separating (6) the first bottom part (4) of thestripping tower (1) and the second bottom part (5) of the stripping tower (1) to obtain a first bottom chamber (4) and a second bottom chamber (5).

19. Apparatus according to claim 18, wherein the means for separating (6) the first bottom part (4) of the stripping tower (1) and the second bottom part (5) of the stripping tower extends from the bottom plate of the stripping tower (1) to a height of the stripping tower (1) not exceeding 2 / 3, preferably 1 / 2, more preferred 1 / 3, of the total height of the inner volume of the stripping tower (1).

20. Apparatus according to claim 18 or claim 19, wherein the means for separating (6) the first bottom part (4) of the stripping tower (1) and the second bottom part (5) of the stripping tower is a separation wall (6), and at an upper level (6a) of the separation wall (6), the cross-section area of the second bottom chamber (5) is larger than the cross-section area of the first bottom chamber (4); and / or wherein, at the upper level (6a) of the separation wall (6), the cross-section area of the second bottom chamber (5) is larger than the cross-section area of the second bottom chamber (5) at lower level of the separation wall (6).

21. Apparatus according to any one of claims 11 to 16, wherein the intermediate outlet (20) and the first outlet (8) are spaced apart by a distance of at least 10%, preferably at least 25%, more preferred at least 50% of the average diameter of the bottom section (3) of the stripping tower (1).26

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